1. Field of Invention
The present disclosure relates to a method of controlling a low-pressure fuel pump for a gasoline direct injection (GDI) engine. More particularly, it relates to technologies which can increase fuel efficiency of a vehicle by variably controlling a low-pressure pump and ensure driving stability of a vehicle by coping with any problematic situation that may occur while increasing the fuel efficiency.
2. Description of Related Art
Since a GDI engine injects a high pressure of fuel into a combustion chamber, a fuel supplying system, including a low-pressure system and a high-pressure system, directly injects fuel through an injector to a combustion chamber, where the high-pressure system gives greater pressure to primary compressed fuel by the low-pressure system.
A low-pressure system of the prior art is typically operated in the manner of driving a low-pressure fuel pump to exhaust fuel at a designed maximum flow rate in the state of maintaining a constant fuel pressure. Because the constant fuel pressure and flow rate are based on the state of significantly coping with various changes caused by a driving situation of a vehicle in the high-pressure system, unnecessary fuel pressure and flow rate are continuously formed in a conventional situation, such that the low-pressure fuel pump is always operated in the overworking state.
Since the low-pressure fuel pump is overworked more than necessary for a GDI fuel supply system, unnecessary energy consumption is caused. Thus, this results in deteriorating fuel efficiency.
Therefore, if a low-pressure fuel pump is variable controlled to provide necessary fuel pressure and flow rate that are suitable to a driving situation of a vehicle in the low-pressure system, energy consumed by the low-pressure fuel pump is reduced, such that fuel efficiency of the vehicle is improved.
FIG. 1 is a block diagram illustrating a low-pressure system of a GDI engine which uses a conventional brushless direct current (BLDC) motor for a low-pressure fuel pump. When an engine controller 500 provides a target fuel pressure to a pump controller 502, the pump controller 502 receives a signal which is fed back through a fuel pressure sensor 506 installed toward a low-pressure fuel pump 504 and controls the low-pressure fuel pump 504 by a PID (Proportional, Integral, Derivative) control, such that the target fuel pressure is pursued.
In view of the pump controller 502, as shown in FIG. 2, the pump controller 502 receives only the target fuel pressure of a low-pressure side from the engine controller 500 and a fuel pressure measured and fed back through the fuel pressure sensor 506, and feed-back controls the low-pressure fuel pump 504.
The above-described fuel pressure control that copes with an amount of consumed fuel is coped in real time if possible and is configured to be able to vary a fuel rate. Thus, compared with the prior art in which a maximum flow rate is always formed, the fuel pressure control reduces a current consumed in the low-pressure fuel pump 504, such that it is achieved to improve fuel efficiency.
However, in case of a GDI engine, problems occur when flow rate provided from a low-pressure system is insufficient or when an insufficient fuel pressure of the low-pressure side, compared with a pressure practically necessary for a high-pressure system, is formed under certain condition due to an unsuitably set target fuel pressure of a low-pressure side. Such problems include engine stop, lighting of an engine warning light, overload rash, poor acceleration.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.